1. Field of the Invention
The invention relates to a device and a method for the operation of a fuel cell with raw-material gases being fed to it on both sides of an electrolytic membrane thereof.
2. Discussion of the Prior Art
By way of example, DE 10 2007 029 596 A1 describes that an electrolyte membrane, which is permeable for protons but is not permeable for electrons, keeps the two raw-material gases, which are fed in continuously, specifically the fuel supplied on the anode side (for example hydrogen) and the oxidant supplied on the cathode side (for example the oxygen contained in the surrounding area) separate from one another in a fuel cell. In particular, the membrane may be in the form of a thin polymer film (in a fuel cell of the PEM type) or in the form of a brittle oxide ceramic (in a fuel cell of the SOFC type).
The invention is based on the discovery that a very thin membrane such as this is highly susceptible to a fracture as a result of steady-state, and to an even greater extent, dynamic pressure differences on both sides of the membrane in the cell. Pressure regulation, which reacts sufficiently quickly and nevertheless without overshooting, of one of the two raw-material gases as a function of the instantaneous feed pressure of the other raw-material gas is, however, highly complex; in particular, neither the outlet valve of a gas cylinder or a fuel reservoir of this type nor the compressor for the air supply can in practice be adjusted sufficiently quickly, continuously and accurately for defined pressure changes. It is particularly critical that, depending on the instantaneous supply and operating circumstances, for example in the event of load changes, the pressure gradient across the membrane may be reversed briefly and at short notice. Synchronous pressure profiles must be maintained not only during the operation of the cell but also when it is being started up at the start of operation and shut down at the end of operation, in order to avoid loads on one side of the membrane, and this is additionally problematic from the operational point of view and can be coped with only to a restricted extent even with a high degree of active control complexity. Any control matching between the two gas pressures which interact with one another is, on the other hand, completely impossible from the installation point of view in the fuel cell itself.
The invention is therefore based on the technical problem of operating a fuel cell more conservatively without any particularly complex additional installation complexity.